Microwave-assisted synthesis and evaluation of naphthalimides derivatives as free radical scavengers

A facile and efficient microwave-assisted reaction of 1,8-naphthalic anhydride derivatives with primary amines, leading to the synthesis of 1,8-naphthalimides, has been developed. Subsequently, the free radical scavenging properties of the 1,8-naphthalimide derivatives were evaluated against 2,2-diphenyl-1-picrylhydrazyl (DPPH^•). The results showed that the scavenging activities of compounds 2a, NBNA, 3b, and 3c were more efficient than that of the common synthetic antioxidant 2,6-diter-butyl-4-methylphenol (BHT), with IC₅₀ values of 61.9, 54.0, 42.2, and 43.1 μM, respectively. The imide groups introduced at position 4 as well as the nitro functionality at position 3 of the naphthalene moiety were the major contributors to the free radical scavenging activities.